#080
Notes on make and makefiles.
Notes
Make is a tool which controls the generation of executables and other non-source files of a program from the program’s source files. Traditionally used for compiling code, but can also be used to automate common tasks.
GNU Make is the standard implementation of Make for Linux and OS X. Common alternatives include BSD Make, Microsoft nmake, and CMake.
The Makefile
Makefiles comprise rules, macros that define the required process. Indent with TAB not spaces!
Rules have the following structure:
target .. : prerequisites ..
recipe
...
Built-In Rules
Run make -p in a folder with no makefile to see the default rules.
See Catalogue-of-Rules Includes:
- Compiling C programs - n.o is made automatically from n.c with a recipe of the form ‘$(CC) $(CPPFLAGS) $(CFLAGS) -c’.
- Compiling C++ programs -n.o is made automatically from n.cc, n.cpp, or n.C with a recipe of the form ‘$(CXX) $(CPPFLAGS) $(CXXFLAGS) -c’.
Implicit-Variables
Pre-defined variables available to make. See Implicit-Variables. Includes:
- CC Program for compiling C programs; default ‘cc’.
- CXX Program for compiling C++ programs; default ‘g++’.
- CFLAGS Extra flags to give to the C compiler.
- CXXFLAGS Extra flags to give to the C++ compiler.
- LDFLAGS Extra flags to give to compilers when they are supposed to invoke the linker
- LDLIBS Library flags or names given to compilers when they are supposed to invoke the linker
Internal Macros / Automatic Variables
See Automatic Variables Includes:
| Macro | Description |
|---|---|
$? |
names of all the prerequisites that are newer than the target |
$@ |
file name of the target of the rule |
$* |
stem with which an implicit rule matches |
$% |
target member name, when the target is an archive member |
$< |
name of the first prerequisite |
Special Target Names
See Special-Targets. Includes:
| Target | Description |
|---|---|
.DEFAULT |
default commands if no matching target |
.IGNORE |
ignore error codes, same as the -i option |
.PRECIOUS |
Files you specify for this target are not removed |
.SILENT |
do not echo commands, same as the -s option |
.SUFFIXES |
suffixes that are meaningful in suffixes rules |
.PHONY |
targets that should be run unconditionally |
Tricks
Compiling c++ to .exe
The exe extension is very ‘DOS/Windows’ and make doesn’t go out of its way for this to be easy with default implicit rules.
But it can be done relatively generically by defining the suitable %.exe: %.cpp rule. e.g.
SOURCES := $(wildcard *.cpp)
TARGETS := $(SOURCES:.cpp=.exe)
.PHONY: all
all: $(TARGETS)
.PHONY: clean
clean:
rm -f $(TARGETS) *.o
rm -fR *.dSYM
%.exe: %.cpp
$(LINK.cpp) $^ $(LOADLIBES) $(LDLIBS) -o $@
.SUFFIXES: .exe
NB: LOADLIBES is a deprecated (but still supported) alternative to LDLIBS, see the manual.